In order to decrease the noise associated with vibration in various industrial machines, vehicles, and appliances, manually applied die-cut mastic or asphaltic sound deadening pads have been employed. The construction of new die-cut pads, which correspond to various part layouts, can be expensive due to the complexity of the parts. Also, the installation and replacement of these deadening pads can be labor intensive since the pads are manually applied.
To decrease vibration noise, vibration damping coatings, including low-frequency, vibration-damping coatings that are epoxy or PVC based, have been employed. However, these coatings often are expensive because of high material costs. Furthermore, such coatings have low sound-damping characteristics and do not fully exceed the benefits of die-cut sound pads for the temperature range between −20° C. and 60° C. The use of these coatings has also raised environmental concerns. Unused or scrap materials from an epoxy-based, liquid-applied sound-damping treatment are considered hazardous waste that requires special disposal methods. Use of a PVC-based coating introduces vinyl chloride into the environment.
Aqueous vibration-damping coatings have also been used to decrease vibration noise. However, the vibration-damping characteristics of known bakeable or air-dried waterborne coatings are adequate only in a narrow temperature range. Such aqueous vibration-damping coatings have been applied by robotic controlled applicator guns, examples of which include airless spray, air-assisted spray, swirl, flow-bar and slit nozzle type applicators. However, such devices cannot apply high surface weight, waterborne compositions in a manner that provides controlled drying. Moreover, when such devices are used to apply a bakeable, waterborne, liquid-applied sound-damping composition to the surface of an object, the sound transmission loss and damping properties of the composition are often compromised.